Climate and water-table levels regulate peat accumulation rates across Europe

PLOS One | https://doi.org/10.1371/journal.pone.0327422 July 23, 2025 9 / 16 rates. This limitation could be attributed to the relatively limited seasonal distinctions within our study areas, which might not encompass the full range of GDD values necessary to establish a connection with peat accumulation definitively. Our research represents the first study using long-term peat accumulation data to examine the correlation between water-table depth and peat growth rates. We observe that the highest aPAR values occur when the water table is between 5 and 10 cm below the peatland surface. In contrast, aPAR tends to be low when the water table is above the surface (< 0 cm, ~standing water) or deeper than 25 cm, likely reflecting reduced plant productivity and increased decomposition losses, respectively. It is interesting that previous studies in peatland research have consistently identified an optimal WTD of approximately 10 cm, albeit with vastly contrasting approaches to this study, and over shorter timescales. Vari- ous studies focusing on the rewetting of peatlands suggest that maintaining a WTD of ~10 cm optimally mitigates green- house gas emissions. Studies include [34,35], drawing from earlier research [36–38], and [39], who refer to an ‘optimal Fig 5. Hexagonally-binned point density plots of aPAR data against mean water-table depth (width = 5 cm on the x-axis). The Loess Smoothing Model (green), Gaussian Response Model (red) and Generalized Additive Model (blue) are illustrated. The dashed line represents a water-table depth of

10 cm. ‘Rugs’ are shown along the axes to illustrate data density. https://doi.org/10.1371/journal.pone.0327422.g005